Sum At Level K : No such element Exception

#1

import java.util.*;
public class Main {
public static void main(String args[]) {

	Tree tree = new Tree();
	Scanner s = new Scanner(System.in);

	int k = s.nextInt();

	System.out.println(tree.sumAtLevelK(k));

	
}


public static class Tree{

	private class Node
	{
		int data;
		ArrayList <Node> children;

		Node(int data)
		{
			this.data = data;
			children = new ArrayList <> ();
		}
	}


	private Node root;


	Tree()
	{
		Scanner s = new Scanner(System.in);
		this.root = buildTree(s);
	}


	private Node buildTree(Scanner s)
	{
		int data = s.nextInt();

		Node node = new Node(data);

		int number = s.nextInt();

		for(int i = 0; i<number; i++)
		{
			Node child = buildTree(s);
			node.children.add(child);
		}

		return node;
	}


	

	public int sumAtLevelK(int k)
	{
		return this.sumAtLevelK(this.root, k);
	}
	private int sumAtLevelK(Node node, int k)
	{
		if(node == null)
			return 0;
		
		int level = 0;
		int sum = 0;
		int size = 0;

		Queue <Node> q = new LinkedList <> ();
		q.add(node);

		while(!q.isEmpty())
		{
			size = q.size();

			while(size-- != 0)
			{
				if(level == k)
				{
					sum += q.poll().data;
				}
				else
				{
					Node temp = q.poll();
					for(int i = 0; i<temp.children.size(); i++)
						q.add(temp.children.get(i));
				}
			}

			level++;
		}

		return sum;
	}
}

}

#2

Hey @arjunsabu99
Code is fine
make static scanner :

import java.util.*;

public class Main {
static Scanner s = new Scanner(System.in);
public static void main(String args[]) {

	Tree tree = new Tree();
//	Scanner s = new Scanner(System.in);

	int k = s.nextInt();

	System.out.println(tree.sumAtLevelK(k));

}

public static class Tree {

	private class Node {
		int data;
		ArrayList<Node> children;

		Node(int data) {
			this.data = data;
			children = new ArrayList<>();
		}
	}

	private Node root;

	Tree() {
		
		this.root = buildTree();
	}

	private Node buildTree() {
		int data = s.nextInt();

		Node node = new Node(data);

		int number = s.nextInt();

		for (int i = 0; i < number; i++) {
			Node child = buildTree();
			node.children.add(child);
		}

		return node;
	}

	public int sumAtLevelK(int k) {
		return this.sumAtLevelK(this.root, k);
	}

	private int sumAtLevelK(Node node, int k) {
		if (node == null)
			return 0;

		int level = 0;
		int sum = 0;
		int size = 0;

		Queue<Node> q = new LinkedList<>();
		q.add(node);

		while (!q.isEmpty()) {
			size = q.size();

			while (size-- != 0) {
				if (level == k) {
					sum += q.poll().data;
				} else {
					Node temp = q.poll();
					for (int i = 0; i < temp.children.size(); i++)
						q.add(temp.children.get(i));
				}
			}

			level++;
		}

		return sum;
	}
}

}

#3

what is wrong in using two Scanners? one inside the tree class and one in main. Why did you make it static

#4

your code Will check
if there are any more integers left in input.
then you got
Exception in thread “main” java.util.NoSuchElementException